Process for devulcanizing india-rubber.



PATENT,

CARL ADOLPH RESEN STEENSTRUP, OF COPENHAGEN. DENMARK, ASSIGNOR- TO AKTIESELSKABET GUMMI REGENERATIONS- SOCIETET. (SYSTEN RESEN -STEENSTRUP.) OF COPENHAGEN,

DENMARK.

PROCESS FOR DEVULCANlZlNG INDIA-RUBBER.

Specification of Letters Patent. I Application filed March 2,1905. Serial No. 248,155-

Patented Sept. 4, 1906.

of devulcanization which does not require a preliminary separation process, and produces a rubber which can be used as a substitute for pure rubber without admixture of the latter for az'py of the purposes to which rubber is put. The waste rubber treated by this process, as wellas the goods made therefrom, show the same homogeneous structure as those from unvulcanized rubber.

For the purpose of the invention thewaste rubber is disintegrated in a suitable machine without preliminary separation and introduced-into a lead-lined digester having a acket and a stirrer. The mass is covered I with an aqueous solution of an alkali or an alkaline earth or a mixture of both. While stirring, hydrofluoric acid is added, and the digester is tightly closed. 'Steam is then introduced into'the jacket, and the mass is thus heated and continuously stirred for four to six hours. The ressure rises to' six to eight atmospheres and ismaintained thereat for four to six hours, during which thestirring is continued. The steam is now out off, and when the pressure has fallen the cover of the digester is removed, and the pasty mass is jigged on a fine sieve and treated-with water until the latter flows away clear. After this washing operation the mass is suspended and dried and is then ready for use.

The proportion of the alkali or alkaline earth to the waste rubber to be treated depends on the content of sulfur in the latter, and the proportion of hydrofluoric acid depends on the-amount of fabric to be destroyed in the rubber.

If the fabric is present in only small proportion, the hydrofiuoric acid may be obtained during the treatment in the digester from fluor-sparintroduced the latter. At the temperature and pressure employed the fluor-spar yields hydrofluoric acid. If,

however, a considerable proportion of fabric is resent, hydrofluoric acid as such must be a ded. For instance, waste rubber contain ing ten percent. of sulfur and thirty per cent.

of fabric insertion would require five per cent. of alkali or alkaline earth and about five per cent. .ofhydrofluoric acid. If the rubber contains ten er cent. of sulfur, but only one per cent. 0 fabric insertion,-there may beadded either five er cent. of alkali and one to two per cent. of ydrochloric acid,

'or three to four per cent. of alkali or alkaline earth and one to three per cent. of fluor-spar.

All sorts of alkalies or alkaline earths may. be used in the method, it being serviceable, however, to 'use nitrates because, for. one thing, they are the cheapest. To give an example, it may be mentioned that especially good results have been obtained by using a mixture of equal parts of hydrate of'lime or calcium hydroxid, Ca(HO) and nitrate of lime, Ca(NO3)2+4H O, and equally good result has been obtained by using a mixture of equal partsof hydrate of soda, NaHO, and

nitrate of soda, NaNO the latter mixture, however, being'more expensive than the for-' mer.

Having thus fully described my invention, what I claim as new, and desire to secure by Letters Patent of the United States, is

1. The process of devulcanizing india-rub-. ber having fabric insertions, which consists in treating the material under action of heat with a devulcamzing agent and simultaneously with hydrofluoric acid as the agent for destruction of the fabric insertions.

2. The process of devulcanizing india-rnbber having fabric insertions, which consists in disintegrating or dividing the material and treating the'same under pressure with a solution of alkali or alkaline earth together with hydrofluoric acid, until the rubber is devulcanized and its fabric insertions destroyed, and then'washing and drying the product.

3. The process of devulcanizing indie-rubber having fabric insertions, which consists in adding to a divided or disintegrated mass of such material a solution of alkali or alkaline earth and hydrofluoric acid in sufficient quantities respectively to devulcanize the period required to devulcanize the rubber rubber and destroy its fabric insertions, and and destroy the fabric insertion, and afterf subjecting said mass together with said solu- Ward Washing and dryin the material.

' tionand acid to the action of heat in a'closed In testimony whereo 5 vessel. I name to this specification in the presence of 4. A process of devulcanlzlnhg iiipdist-rubtwo subscribing Witnesses. ber havlng fabric insertions, W ic consists in'supplying an aqueous alkaline solution and CARL BH BESEN T T- hydrofluoric acid to the mass of divided in- W1tnesses: f 10 die-rubber -in a closed vessel, heating the MARCUS M6LLER,-

mass and stirring the same for a protracted MAGNUs JENSEN.

I'have signed my I 5 

